In some applications, for instance cable lines, the angle of the loop might be less than
60°. In these applications, the settings of fault resistance coverage in forward and
reverse direction, RFltFwdPG and RFltRevPG for phase-to-ground faults and
RFltRevPP and RFltRevPP for phase-to-phase faults have to be increased to avoid that
FDPSPDIS (21) characteristic shall cut of
f some part of the zone characteristic. The
necessary increased setting of the fault resistance coverage can be derived from
trigonometric evaluation of the basic characteristic for respectively fault type.
Phase-to-ground fault in forward direction
M13142-6 v7
With reference to figure
117, the following equations for the setting calculations can be
obtained.
Index PHS in images and equations reference settings for Phase
selection with load encroachment function FDPSPDIS (21) and index
Zm reference settings for Distance protection function (
ZMQPDIS, 21).
Section 8 1MRK 504 163-UUS A
Impedance protection
250 Transformer protection RET670 2.2 ANSI
Application manual
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